Individuals who are training for physical fitness or athletic competition may wish to improve the efficiency of their cardiovascular systems for improved health and stamina. Continued exposure to the reduced concentration of oxygen in the atmosphere at higher altitudes provides increased mass of red blood cells, improved efficiency of oxygen use by the muscles, and enhanced lung performance. Individuals may wish to be able to obtain the benefits of training in any desired setting. Individuals may further wish to train in any desired setting without being affected by the air quality present in such a desired setting.